ext2: avoid rec_len overflow with 64KB block size

With 64KB blocksize, a directory entry can have size 64KB which does not
fit into 16 bits we have for entry length.  So we store 0xffff instead and
convert the value when read from / written to disk.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 05d9342bb64ee271586f0a9f136e36f599b8cf83..d868e26c15eba90e48c5c1324c9f207ef109d1e6 100644 (file)
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -28,6 +28,24 @@
 
 typedef struct ext2_dir_entry_2 ext2_dirent;
 
+static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
+{
+       unsigned len = le16_to_cpu(dlen);
+
+       if (len == EXT2_MAX_REC_LEN)
+               return 1 << 16;
+       return len;
+}
+
+static inline __le16 ext2_rec_len_to_disk(unsigned len)
+{
+       if (len == (1 << 16))
+               return cpu_to_le16(EXT2_MAX_REC_LEN);
+       else if (len > (1 << 16))
+               BUG();
+       return cpu_to_le16(len);
+}
+
 /*
  * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
  * more robust, but we have what we have
@@ -106,7 +124,7 @@ static void ext2_check_page(struct page *page)
        }
        for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
                p = (ext2_dirent *)(kaddr + offs);
-               rec_len = le16_to_cpu(p->rec_len);
+               rec_len = ext2_rec_len_from_disk(p->rec_len);
 
                if (rec_len < EXT2_DIR_REC_LEN(1))
                        goto Eshort;
@@ -204,7 +222,8 @@ static inline int ext2_match (int len, const char * const name,
  */
 static inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
 {
-       return (ext2_dirent *)((char*)p + le16_to_cpu(p->rec_len));
+       return (ext2_dirent *)((char *)p +
+                       ext2_rec_len_from_disk(p->rec_len));
 }
 
 static inline unsigned 
@@ -316,7 +335,7 @@ ext2_readdir (struct file * filp, void * dirent, filldir_t filldir)
                                        return 0;
                                }
                        }
-                       filp->f_pos += le16_to_cpu(de->rec_len);
+                       filp->f_pos += ext2_rec_len_from_disk(de->rec_len);
                }
                ext2_put_page(page);
        }
@@ -425,7 +444,7 @@ void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
 {
        loff_t pos = page_offset(page) +
                        (char *) de - (char *) page_address(page);
-       unsigned len = le16_to_cpu(de->rec_len);
+       unsigned len = ext2_rec_len_from_disk(de->rec_len);
        int err;
 
        lock_page(page);
@@ -482,7 +501,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
                                /* We hit i_size */
                                name_len = 0;
                                rec_len = chunk_size;
-                               de->rec_len = cpu_to_le16(chunk_size);
+                               de->rec_len = ext2_rec_len_to_disk(chunk_size);
                                de->inode = 0;
                                goto got_it;
                        }
@@ -496,7 +515,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
                        if (ext2_match (namelen, name, de))
                                goto out_unlock;
                        name_len = EXT2_DIR_REC_LEN(de->name_len);
-                       rec_len = le16_to_cpu(de->rec_len);
+                       rec_len = ext2_rec_len_from_disk(de->rec_len);
                        if (!de->inode && rec_len >= reclen)
                                goto got_it;
                        if (rec_len >= name_len + reclen)
@@ -518,8 +537,8 @@ got_it:
                goto out_unlock;
        if (de->inode) {
                ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
-               de1->rec_len = cpu_to_le16(rec_len - name_len);
-               de->rec_len = cpu_to_le16(name_len);
+               de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
+               de->rec_len = ext2_rec_len_to_disk(name_len);
                de = de1;
        }
        de->name_len = namelen;
@@ -550,7 +569,8 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
        struct inode *inode = mapping->host;
        char *kaddr = page_address(page);
        unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
-       unsigned to = ((char*)dir - kaddr) + le16_to_cpu(dir->rec_len);
+       unsigned to = ((char *)dir - kaddr) +
+                               ext2_rec_len_from_disk(dir->rec_len);
        loff_t pos;
        ext2_dirent * pde = NULL;
        ext2_dirent * de = (ext2_dirent *) (kaddr + from);
@@ -574,7 +594,7 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
                                                        &page, NULL);
        BUG_ON(err);
        if (pde)
-               pde->rec_len = cpu_to_le16(to - from);
+               pde->rec_len = ext2_rec_len_to_disk(to - from);
        dir->inode = 0;
        err = ext2_commit_chunk(page, pos, to - from);
        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
@@ -610,14 +630,14 @@ int ext2_make_empty(struct inode *inode, struct inode *parent)
        memset(kaddr, 0, chunk_size);
        de = (struct ext2_dir_entry_2 *)kaddr;
        de->name_len = 1;
-       de->rec_len = cpu_to_le16(EXT2_DIR_REC_LEN(1));
+       de->rec_len = ext2_rec_len_to_disk(EXT2_DIR_REC_LEN(1));
        memcpy (de->name, ".\0\0", 4);
        de->inode = cpu_to_le32(inode->i_ino);
        ext2_set_de_type (de, inode);
 
        de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
        de->name_len = 2;
-       de->rec_len = cpu_to_le16(chunk_size - EXT2_DIR_REC_LEN(1));
+       de->rec_len = ext2_rec_len_to_disk(chunk_size - EXT2_DIR_REC_LEN(1));
        de->inode = cpu_to_le32(parent->i_ino);
        memcpy (de->name, "..\0", 4);
        ext2_set_de_type (de, inode);

diff --git a/include/linux/ext2_fs.h b/include/linux/ext2_fs.h
index c77c3bbfe4bb480c273a72f89bad409fa23609d0..0f6c86c634fd601482c6cca840999b89c5ca4b4f 100644 (file)
--- a/include/linux/ext2_fs.h
+++ b/include/linux/ext2_fs.h
@@ -561,6 +561,7 @@ enum {
 #define EXT2_DIR_ROUND                         (EXT2_DIR_PAD - 1)
 #define EXT2_DIR_REC_LEN(name_len)     (((name_len) + 8 + EXT2_DIR_ROUND) & \
                                         ~EXT2_DIR_ROUND)
+#define EXT2_MAX_REC_LEN               ((1<<16)-1)
 
 static inline ext2_fsblk_t
 ext2_group_first_block_no(struct super_block *sb, unsigned long group_no)